Does comments slow down processing a lot

I'm programming large web solutions here and a new programmer has given me a warning about how much comments i put in my code and said that it could probably lower effiency when parsing and executing the php code in my documents. So my questions are: Does putting huge amount of comments in a file really lower the parsing, compilation and execution time? Using Zend Optimizer, which is the case right now, would it be better if it did slow down the code? Thank you in advance Mathieu Dumoulin www.groupimage.com Web solution Programmer/Analyst